Accepting the Need for Overkill in
Infection Control

read with detached bemusement and sad familiarity the
letters to the editor and other recent writings of Dr. John Hardie in this journal, and
the voices of others on a national, provincial and local level that seek to dilute the
importance of strict infection control in dentistry. It reminds me of recurring,
frustrating conversations I have with a dear friend I have known since childhood. She is a
university-educated mother of four who firmly believes that standard immunizations are
dangerous; that fluoride in the water causes cancer; that AIDS was a government experiment
gone bad; that the military is hiding the truth about UFOs and a variety of other
anti-science rantings commonly found in newsgroups such as alt.folklore.urban and other
nefarious places on the Internet.

The fact that individuals may have agendas to promote and somehow acquire platforms
from which to proclaim them does not, in and of itself, prove that any sort of controversy
actually exists. Only in the past decade and a half or so has dentistry finally arrived at
a place in infection control where the rest of the health sciences in the industrialized
world have been for nearly a century. The idea that such basic concepts as aseptic
procedures (i.e. universal precautions) are being questioned by influential people in our
profession is an embarrassment to dentistry as a whole and would certainly be unthinkable
in other health care settings.

Yes, performing dentistry while practising proper infection control according to CDA,
ODA, RCDS, ADA, CDC, OSAP, OSHA or whatever acronymical authority we ascribe to this month
has definitely made our practices and our lives more complicated. However, the modern
reality is that the health care professional community needs no further impetus to prove
that dentistry should now be doing what we should have been doing decades ago when it was
discovered that hepatitis B is caused by a virus that can be found in the blood and
saliva.

I have grown weary of hearing the rhetoric mantra, Wheres the scientific
proof?, with regard to infection control in dentistry. Well, they can
pull out their list of references and I can pull out mine. Consider the following brief
sampling:

We KNOW that many viruses are not as easy to inactivate as we once thought.1

We KNOW that live blood cells, bacterial and viral particles can survive inside our
handpieces even after thorough disinfection.2

We KNOW that handpieces inject material into tissue.3

We KNOW that our dental unit waterlines and evacuation system lines are grossly
contaminated.4

We KNOW that patients can easily suck bacteria back through saliva ejectors.5

We KNOW that cross-contamination of X-ray films can occur in the processor.6

We KNOW that toothbrushes and dentures can transmit disease.7

We KNOW that no disease reporting system exists that is capable of detecting widespread
low frequency cross-infection.8

We KNOW that infectious patients lie to us about their infections.9

What more evidence could we possibly need of the necessity for strict infection
control, including standard and universal precautions, in dentistry? Evidence may not be
absolute proof, but it certainly is the basis of most of the scientific clinical decisions
we make every day.

What sort of scientific experimental design will it take to convince those still
waiting for scientific proof; those that decry the lack of scientific
evidence? Researchers will have to: first, radioisotope label a virus (this is
currently technically impossible); second, infect someone with this theoretical virus
(this would never get through an ethics committee); third, perform a dental procedure on
this patient, and then, without properly sterilizing all the equipment and instruments in
between procedures, perform another dental procedure on another person using the same
equipment (again, ethics committee problems) in order to detect the same technically
impossible, theoretically labeled virus. Well they may as well quit waiting: such
experiments will never happen.

While we must always strive to practice evidence-based infection control, the reality
is that the level of evidence may not always be as strong as we would like it to be. One
of the biggest gaps in our infection control knowledge is knowing the risk of acquiring an
infectious disease in a given situation. If such risks could be known, they would help
justify the importance of, or need for, a particular infection control procedure.

There are two aspects to consider with such risks. One is the risk of
cross-contamination (the transfer of microbes from one person to another). The other risk
is of cross-infection (the actual occurrence of infection following cross-contamination).

If there is evidence of cross-infection, then one knows that cross-contamination must
have occurred. Likewise, if cross-contamination occurs, there is some potential for
cross-infection. We would all like to have cross-infection evidence as the basis for using
a given infection control procedure. For example, the evidence for the involvement of
sharps injuries in cross-infection of bloodborne diseases provides a solid and
unquestioned foundation for using infection control procedures to prevent sharps injuries
among health care workers.

Unfortunately, we do not have such strong evidence to support all of the
recommendations for infection control. We must, instead, rely on cross-contamination data
that, at least, establishes some degree of potential for cross-infection. For example,
while less information exists about cross-infection in dentistry involving ungloved hands,
dental aerosols, contaminated dental unit water or contaminated dental operatory surfaces,
it is clear that all of these can involve cross-contamination and, therefore, some
potential for cross-infection.

Since we can neither predict nor measure all situations that will cause a
cross-contamination to result in a cross-infection, a certain amount of overkill is built
into modern infection control recommendations to assure the best protection for patients
and dental health care workers. Performing infection control to reduce cross-contamination
gives the body a better chance to defend itself against infectious agents.

The bottom line is that we do not always know when we may be exposed to potentially
virulent microbes. We never know the exact composition of a source of microbes involved in
contamination of an environmental surface, dental unit water or air, saliva, blood or
skin. We do not know when the entrance of microbes into the body may be enhanced through
unrecognized breaks in the skin or mucous membranes. We do not know when our resistance to
a given microbe may be low.

All of these unknowns tend to foster a certain level of overkill at all
stages in infection control. The absolute science may not be there, but we are a
profession that holds the safety of our patients in our hands. We need to err on the side
of caution. The best defense is a good offense; we need to be too safe. I would rather
that than, in the interests of saving money or not seeming foolish or fearful or whatever
our excuses have been, to find out at some later date that we were not safe enough.

The Latin phrase, primum non nocere applies as always: our first concern should
be to do no harm. Some people may call it overkill; I call it being safe. Our approach to
overkill in the absence of confirmatory science is best summarized by what my grandfather
always told me: It is better to be safe than sorry.

Dr. Petty is the director of dentistry and oral medicine at the Foothills
Medical Centre and director of oral medicine and surgery at the Tom Baker Cancer Centre in
Calgary, Alberta. He is past-chair of the CDA Committee on Community and Institutional
Dentistry and author of the CDAs Workbook on Infection Control.

The views expressed are those of the author and do not necessarily reflect the opinion
or official policies of the Canadian Dental Association.